ORCID

http://orcid.org/0000-0001-5151-1765

Date of Award

Spring 5-15-2019

Author's School

Graduate School of Arts and Sciences

Author's Department

Chemistry

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Solid-state NMR spectroscopy is a useful structural tool, with a high sensitivity to the local atomic-scale environment providing a powerful probe of structure, disorder, and dynamics of solids. In this dissertation, solid-state NMR was used to characterize chemisorbed products of solid amine sorbents exposed to CO2. Solid amine sorbents are promising candidates to capture CO2 for the purposes of mitigation of this greenhouse gas in high-concentration sources, such as flue gases emitted from power plants or industrial sites. Understanding the adsorption process of these solid materials is critical to help design better materials to have a higher CO2 uptake.

A series of solid-state NMR methods were employed to study these materials.15N CPMAS of primary amines (APS) before and after 13CO2 was employed, and the result is informative. With the time-evolution of signals before and after CO2 exposure, the decreased intensity of the reactant resonance and increased intensity of the products’ resonances, we were able to assign amine, ammonium, and carbamate in 15N spectra. Complementary 13C{15N} REDOR and 15N{13C} REDOR of a primary amine (APS) were used to obtain the 13C-15N dipolar interaction of the chemisorbed product species corresponding the distances of both directly-bonded C-N of carbamate and the distant interaction between of carbamate to its ammonium counter ion that is ion-paired to it.

Under humid (or damp) conditions, hydrated bicarbonate was found in three types of amine: primary, secondary, and tertiary. NMR measurements show the hydrated bicarbonate undergoes dynamic motion at room temperature induced by surrounding water. Different water environments lead to chemically-inequivalent bicarbonates, which results in two 13C signals when bicarbonate is cooled down (100 K). Exposure to D2O, replacing water, allowed for interactions between the two bicarbonate species and the surrounding environments to be elucidated, via low-temperature 13C-1H HETCOR.

Additionally, dynamic nuclear polarization (DNP) NMR was successfully performed on primary amines (APS). 2D DNP HETCOR was used to determine the interactions between carbamate pendant molecules and the surrounding environment. 13C-1H HETCOR, 15N-1H HETCOR, and 29Si-1H HETCOR (all using enhancements provided by DNP) were performed, and the results show coupling between carbamate and the hydroxyl groups on the SBA15 (silica) surface.

Language

English (en)

Chair and Committee

Sophia E. Hayes

Committee Members

Julio D’Arcy, Alexander Barnes, Jonathan Barnes, Daniel Giammar,

Comments

Permanent URL: https://doi.org/10.7936/mvv8-r597

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